Currently, in the fabrication of titanium and titanium-alloy articles, thermal or heat-treating processes are included in the manufacturing process. These steps are to ensure that material grain size associated with the article's microstructure is produced and maintained at a level that is as small as possible. The resulting material grain size of the formed article is critical to both its ductility and strength among other properties. In general, grain sizes larger than or equal to those identified as a number 6, i.e., less than or equal to a number 5 as defined by ASTM E 112 (larger than about 75 μm) are not desirable for most mechanical work or forming operations. As such, it is the normal practice to employ a full annealing, i.e. recrystallization, or at least stress-relieving heat-treatment steps in conjunction with any cold or hot work or forming performed on the article.
There have been exhaustive attempts to eliminate the thermal treatment, or heat treating, manufacturing process steps, which can account for up to approximately 20% of the costs not to mention processing cycle time associated with producing a titanium or titanium-alloy article or fastener, such as either a deformable-shank solid rivet or non-deformable-shank lockbolt, threaded pin, etc.
The heat-treated articles are then typically installed with a wet sealant applied to their surfaces to protect the articles and surrounding structure from corrosion. The process of wet sealing also accounts for a significant portion of the costs of installing metal and metal-alloy components or articles, and represents an extra process step requirement, which slows the installation procedure.
Because heat treatment and wet sealing are both costly and time-consuming steps in the manufacture and installation of titanium and titanium-alloy material articles, it would be desirable to provide a process for forming titanium and titanium-alloy material articles having smaller grain sizes while reducing the number of associated processing steps required. Further, it would be desirable to provide a process of installing titanium and titanium-alloy material articles without having to apply wet sealants.